More samples than sample rate

[MAX_JD]

I am trying to read back the current from several devices using a NI 9227, I specifically want a sampling frequency of 50Hz to provide parity with other measurement methods being used.

I am using a DAQ assistant to capture the data.  when I run my code I appear to be getting significantly more samples than the 50Hz sample rate would produce.  I was getting almost 100000 samples in one minute when I should only be getting 3000. I thought perhaps I needed a wait to only capture once a second but this only produced an overflow.

I have set my samples to capture to 50 and my frequency to 50Hz which I thought would mean that every second I would process those samples but it is happening far quicker.  I am probably missing something obvious but I am very confused as to why I am getting so many samples.

thanks for any help

[Kevin_Price · Accepted solution]

See the manual, page 17.  The minimum supported sample rate is ~1613 Hz, which is what you'll actually get when you request a lower sample rate like 50 Hz.  Hence the 100k samples in 60 seconds.

-Kevin P

[MAX_JD]

Ha It never occurred to me there would be such a high minimum sample rate that explains it thanks